Aging-informed behavior of Sn3.8Ag0.7Cu solder alloys

Predicting reliability of solder joints requires a thorough understanding of solder constitutive behavior. Recent studies on SnAgCu solder alloys have reported that pre-test conditions of aging-time and aging-temperatures can be factors that significantly affect solder constitutive behavior. The results presented here are a part of ongoing efforts to construct constitutive models that can predict aging affects on behavior of SnAgCu solder alloys. In this work, creep test results on aged Sn3.8Ag0.7Cu samples are reported, and aging effects are discussed primarily on secondary creep behavior and on microstructure. Aging effects on primary creep are observed, and will be discussed, and modeled in a future work. Experiments to characterize behavior were carried out using double-lap shear tests on specimens specifically prepared to represent realistic microstructures, and mitigate effects of joint geometry, and stress heterogeneity during test conditions. Aging temperatures of -10deg C, 25deg C, 75deg C and 125deg C, and aging times of 15, 30, 60 and 90 days (at each aging temperature) were selected as different levels of factors in a statistically designed experiment. Previous studies have focused on developing constitutive models without due considerations to aging effects, the results presented herein augment aging-informed constitutive model development efforts that are currently in progress.